This disclosure teaches methods for achieving alignment of liquid crystal (LC) using graphene layers.
This disclosure teaches concurrent creation of alignment layers and electrodes using graphene for controlled reorientation of LC by an electric field.
This disclosure teaches a new product comprising graphene layers as both alignment layers and electrodes.
Electro-optic LC devices can be transmissive (for example, displays), reflective (for example, tunable filters), or refractive (for example, waveguides such as steerable electro-evanescent optical refraction devices).
The principle mechanism of these devices relies on two factors: the ability of the surface to homogeneously align liquid crystals and the ability of that alignment to change with an applied electric field.
These two requirements are usually fulfilled by electrodes with relatively low transmission losses that are deposited on parallel substrates and a LC aligning layer between the electrodes and the LC.
In a conventional LC cell, indium tin oxide layers serve as the electrodes and polyimide layers with unidirectional rubbing direction serve as the aligning layers of the LC director at the two substrates. A wide range of conductive materials and (in)organic materials have been developed and demonstrated as effective electrodes and alignment layers for LC, respectively.
While these conductive and alignment layer combinations work for the majority of LC-based transmissive applications due to short path lengths (˜μms), an ideal scenario is where the two functions are met with a single layer of material.
In certain architectures, such as a slab waveguide with an LC-cladding, additional layers of material introduce unwanted absorption and scattering losses over relatively long path lengths (˜cms), thereby significantly degrading throughput.
Reducing the conductive and aligning functions with a single layer of material offers the potential to minimize these losses and optimize throughput of light over a wide range of spectral bands. Graphene, the two-dimensional form of carbon, is an ideal material to fulfill the role as both an LC electrode material and an aligning layer.
We demonstrate the first use of graphene being concurrently used as the electrode and the alignment layer.